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65 Cards in this Set
- Front
- Back
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What must respiratory muscle overcome to ventilate?
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Airway resistance
Elastic resistance of the lung and chest wall tissues |
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What is pleural pressure?
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Pressure of the fluid in the space between the lung pleura and the chest wall
Slightly negative – allows suction Negative pressure increases with expansion Lung volume increases pleural pressure decreases |
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What is alveolar pressure?
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Pressure of the air inside the lungs
= atmospheric pressure when there is no air movement Falls during inspiration Increases during expiration |
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What is transpulmonary pressure?
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The difference between the alveolar pressure and the pleural pressure (indicates recoil pressure)
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What is lung compliance?
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How much the lungs expand for each unit of increase in transpulmonary pressure
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How is lung compliance determined?
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Elastic force of the lung tissue – elastin and collagen
Elastic forces caused by the surface tension of the fluid lining the inside walls of the alveoli Water molecules attempt to contract and collapse the alveoli |
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What is surfactant made of?
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Phospholipids, proteins and ions
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Where is surfactant produced?
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Type II alveolar epithelial cells
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What is the function of surfactant?
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Reduces the surface tension by dissolving partially in the fluid lining of the alveolar surface
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What is spirometry?
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Records changes in pulmonary volume
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What is tidal volume?
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Volume of air inspired or expired with each normal breath (500ml)
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What is inspiratory reserve volume?
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Extra volume of air that can be inspired above the normal tidal volume when a person inspires with full force
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What is expiratory reserve volume?
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Maximum extra volume of air that can be expired by forceful expiration after normal tidal expiration
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What is residual volume?
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Volume of air remaining in the lungs after the most forceful expiration
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What is inspiratory capacity?
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Tidal volume plus inspiratory reserve volume = the amount of air a person can breath in
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What is functional residual capacity?
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Expiratory reserve volume plus the tidal volume
= amount of air left in the lungs after normal expiration |
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What is vital capacity?
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Expiratory reserve volume plus the tidal volume = maximum amount of air a person can expel from their lungs after first filling the lungs to their maximum extent
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What is Total lung capacity?
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Vital capacity plus the residual volume = maximum volume to which the lungs can be expanded with the greatest possible effort
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What is Minute respiratory volume?
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Total amount of new air moved into the respiratory passages each minute
= tidal volume x respiratory rate per minute Normally about 6L |
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What is Alveolar ventilation?
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The rate at which new air reaches gas exhange areas
Affected by dead space air - air which never reaches gas exchange areas but simply refills passages - reduces efficiency of expiratory gas removal |
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How do you calculate the rate of alveolar ventilation?
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= Respiratory rate x the amount of new air entering these areas with each breath
- 4200ml/minute Total volume of new air entering the alveoli and adjacent gas exchange areas each minute |
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What is partial pressure of gases?
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The pressure exerted by an individual gas in a mixture of different gases
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What does partial pressure influence?
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The rate of diffusion
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What is partial pressure of a gas in a fluid?
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In a solution the partial pressure of a gas is determined by its concentration and solubility coefficient
The pressure exerted by a gas depends on its concentrations of free molecules |
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What is Henry's law? And what does it relate to?
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Henry's law =
Partial pressure = concentration of dissolved gases/ solubility co-efficient Relates to partial pressure of a gas in fluid |
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What is net diffusion of gases between the alveoli and pulmonary blood determined by?
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Partial pressures of oxygen and carbon dioxide
Oxygen - greater partial pressure in the gas phase --> diffuses from alveoli to blood Carbon dioxide - greater partial pressure in the dissolved state in the blood --> so it moves from the blood to the alveoli more readily |
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What is the importance of vapour pressure of water?
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Humidifies respiratory passages that the air enters - (air is also warmed at this stage)
47mmHg at body temperature |
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What is the composition of alveolar air?
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More humid than atmospheric air
Less oxygen More carbon dioxide Alveolar air is replaced slowly by atmospheric air to prevent sudden changes in gas concentrations in the blood |
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What is alveolar PO2 determined by?
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Rate of absorption into the blood and
the rate of entry of new oxygen into the lungs |
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What is alveolar PCO2 determined by?
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Increases directly in proportion to the rate of carbon dioxide excretion and
In inverse proportion to alveolar ventilation |
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What are the layers of the alveolar membrane?
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Alveolar fluid with surfactant
Alveolar epithelium Epithelial basement membrane Interstitial space Capillary basement membrane - can be fused to the alveolar epithelial basement membrane Capillary endothelial membrane |
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What are some factors affecting rate of gas diffusion through the respiratory membrane?
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Thickness of membrane
Surface area of membrane Diffusion coefficient of the gas over the membrane Partial pressure difference of the gas on each side of the membrane |
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What are some factors that may increase the thickness of the respiratory membrane?
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Increased pathologically in pulmonary oedema
Increase pathologically in fibrosis |
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What is a condition where surface area of the respiratory membrane may be altered?
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Decreased pathologically in emphysema
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What can alter the diffusion coefficient of the gas over the respiratory membrane?
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Increased during exercise
CO2 diffuses 20 times as rapidly as O2 |
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What is ventilation perfusion ratio?
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Reflects the match up of where air is getting to and where blood is going.
V/Q = 0 then there is no ventilation in the alveoli V/Q - infinity then there is no capillary blood flow to the alveoli |
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What could cause a V/Q mismatch?
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Less than normal:
Physiological shunt - there is inadequate ventilation to fully oxygenate capillary blood Greater than normal: Physiological dead space - wasted ventilation because it doesn't reach the blood |
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In COPD what would you find in a V/Q ratio?
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Increase and decrease in different areas because of the breakdown of alveolar walls --> there is wasted ventilation because of the breakdown of alveolar walls --> there is inadequate ventilation because of obstruction of small bronchioles
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How oxygenated is alveolar blood?
How oxygenated is blood that passes through the bronchial circulation to supply the tissues? What is the concentration in the pulmonary veins where this blood meets? |
Alveolar = 140mmHg
Bronchial circulation = 40mmHg Venous admixture of the blood = 95mmHg |
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What lung condition may mimic aortic aneurysms?
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Aneurysms of the bronchial arteries
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What is the difference between the bronchial arteries and pulmonary arteries?
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The bronchial arteries supply the lungs with oxygenated blood.
The pulmonary arteries supply the lungs with deoxygenated blood to be reoxygenated in the alveoli |
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What causes movement of oxygen from capillaries to the peripheral tissues?
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High PO2 in the arteries (95mmHg) and low PO2 in the interstitial fluid (40mmHg) creates a concentration gradient.
Initially rapid diffusion of O2 into the peripheral tissue occurs. Oxygen is constantly being used up in the tissue so it can create a huge pressure gradient. |
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What causes movement of oxygen from capillaries to the peripheral tissues?
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CO2 moves to the interstitium and then the capillaries because there is a high concentration in the cells - it is constantly being made
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What diffuses faster CO2 or O2?
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CO2 diffuses 20 times faster!
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What is the role of haemoglobin in respiration?
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Oxygen carrier.
Stabilises O2 pressure in the blood and maintains a nearly constant PO2 in the tissues by only allowing efficient dissociation of O2 from the Hb if the tissue PO2 is 40mmHg or less |
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What part of haemoglobin does O2 bind to?
Does it bind loosely or tightly? Does it bind reversible or irreversibly? |
Heme
Loosely Reversible |
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Oxygen-Haemoglobin Dissociation curve
What does it indicate? |
Oxygen binds to haem more easily as the number bound increases.
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What factors can shift the oxygen-haemoglobin dissociation curve?
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Shift to the right:
- Increased hydrogen ions - decreased pH - Increased CO2 - Increased temperature - Increased BPG |
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How does BPG affect the oxygen haemoglobin dissociation scale?
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BPG or DPG - has a high affinity for binding to deoxygenated haemoglobin. It therefore promotes the release of oxygen in to the tissue.
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What is the Bohr Effect?
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The effect of increase CO2 in the tissues causes dissociation of O2 from Hb and uptake into the blood.
CO2 diffuses from tissue into the blood. Bloock pH decreases because of increase in H2CO3. Dissociation curve shifts to the right forcing O2 away from the Hb and increasing the amount of O2 delivered to the tissues. |
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How is CO2 transported in the blood?
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70% as carbonic acid
(some dissociates into hydrogen and bicarbonate ions) The rest becomes carbaminohaemoglobin as it combines with Hb and plasma proteins |
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What is the Haldane effect?
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Binding of oxygen with Hb in the lungs displaces carbon dioxide from the blood, into the alveoli.
OxyHb is a stronger acid than Hb -which binds CO2 less strongly |
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Where is the respiratory centre found?
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In the dorsal respiratory neurons of the medulla oblongata - nucleus of the solitary tract
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Which cranial nerves terminate at the dorsal respiratory neurone?
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CN IX and X
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What does the respiratory centre receive inputs from?
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Peripheral chemoreceptors
Baroreceptors Lung and chest wall mechanoreceptors |
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How does the respiratory centre work?
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Generates a rhythmic ramp signal to the diaphragm which causes inspiration then ceases activity for expiration
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How does this rhythmic respiratory ramp control inspiratory rate and depth?
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Rate of the ramp increase is controlled
The limiting point at which the ramp suddenly ceases is also controlled, monitoring the rate of respiration. |
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What does the pneumotaxic centre of the pons do?
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Transfers signals to the inspiratory area
Switches off the inspiratory ramp, controlling the duration of the filling phase of the lung cycle |
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What does the ventral medullary group do?
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Little role in quiet breathing
It is activated by the dorsal horn group when respiratory drive is increase Signals to the abdominals for forced expiration Provides overdrive when high rates of ventilation are required |
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What other brain areas may affect respiration?
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Limbic system and hypothalamus
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Hering-Breur inflation reflex - what is it and what is its role?
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Stretch receptors in the bronchi send impulses via the vagus nerve to the dorsal respiratory group, switching the inspiratory ramp off
Has a role in deep breathing |
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What are the chemical factors controlling respiration?
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CO2 concentration
Stimulation of the chemosensitive areas of the respiratory centre by H+ ions - the chemosensitive areas are located bimanually in the medulla. CO2 crosses the BBB and is converted into H+ |
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How long does it take for increased CO2's effect on the respiratory centre to decrease?
What causes this adjustment? |
1-2 days
Renal readjustment of hydrogen ion concentration Bicarbonate begins to cross the BBB and returns H+ levels to normal by combining with it. |
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What is oxygens role in respiratory control?
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The peripheral chemoreceptors detect changes in this.
Send signals to the dorsal respiratory group Chemoreceptors become strongly stimulated when the arterial oxygen concentration drops below normal Also stimulated by O2 increases |
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Where are the peripheral chemoreceptors located?
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Bifurcation of the carotids
Some in the aortic bodies Only exposed to arterial PO2 |
